Post subject: Blowing air at the motherboard with a fan inside the case

Posted: Sat May 03, 2014 9:13 am

Joined: Sat May 03, 2014 8:32 amPosts: 2

I have a first generation Antec Sonata case. I chose it for quietness, but never tried to modify it to make it really quiet. Noise sources inside were the 120 mm rear fan, the stock CPU cooler, the PSU fan, and the hard drive. Most noise is from airflow, and the rear fan, which is probably getting a bit louder from age now.

I just did an experiment, adding a 120 mm fan inside the case blowing at the motherboard. It's mounted on two angle brackets connected to two 120 mm fan mounting holes on the hard drive cage, with rubber grommets for vibration isolation. (Normally, the fan there is meant to be mounted on 4 holes for blowing air front-to-back.) I'm running it at only 5 volts, and it's almost silent. It's making a big difference in northbridge heat sink and memory heat spreader temperatures. The northbridge heat sink used to be so hot it was painful to keep my finger on it, and now it's just a bit warm. The sensor differences are less impressive, but temps are down a few celsius.

The theory behind this is that all the empty space in the case provides a low resistance path for airflow, and all the stuff sticking out from the motherboard slows airflow there. The added fan makes air flow by the motherboard, cooling it better. Bringing in air from the outside should provide better cooling, but it would also require cutting a hole in the case and probably result in more noise

I wonder what others think of this idea?

It seems I could change the exhaust fan from medium to low speed now, which greatly quiets the case, leaving the CPU fan as the most prominent noise source when it speeds up. I'm still a bit afraid to leave it that way though, wondering if some hot spots might form. I'm also wondering whether to replace it with a low noise version and/or modify the case to improve air intake.

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Post subject: Re: Blowing air at the motherboard with a fan inside the cas

Posted: Sat May 03, 2014 11:29 am

Joined: Sat May 12, 2012 10:14 amPosts: 7Location: Slovenia

For acoustic improvements you have to do just the basic stuff:- suspend the HDD under the optical drive,- downvolt the Tricool 120 fan with the 12-7 volt trick or replace with a better fan- put an aftermarket heatsink on the CPU- undervolt or replace the PSU fan- put the clutter of wires and cables in the upper chamber

With my experimentations with multiple fans in a case I observed a strange effect of worse teperatures of other components that were not in the path of airflow of the additional fan. Maybe because of the counterproductive effect against the airflow from front passive intake and rear fan creating some hot spots?

I did this in my Antec 300 and with only one fan i reached better acoustics and overall better teperatures at IDLE.On my Gigabyte board I did undervolt in BIOS (ctrl + F1 command for advanced bios) the MCH chip.

Post subject: Re: Blowing air at the motherboard with a fan inside the cas

Posted: Sat May 03, 2014 11:51 am

Joined: Sat May 12, 2012 10:14 amPosts: 7Location: Slovenia

I have a feeling that you are not going to put that much effort on an old system like yours...Are you willing to put some time in software fan managing? Like Speedfan for the cpu stock fan and Rivatuner fot the tiny nvidia fan?

Can you put the additional fan against the hdd cage to blow onto the gpu? The big heatspreader for the northbridge is not a concern.What temps do you have?

Post subject: Re: Blowing air at the motherboard with a fan inside the cas

Posted: Sun May 04, 2014 9:00 am

Joined: Sat May 03, 2014 8:32 amPosts: 2

I don't want to invest much money into stuff that won't be useful if I upgrade, but I'm willing to invest time and effort. That could be interesting and I could learn something.

I'd like to focus on the prominent noise sources first rather than handling everything at once. The fans on the Antec EarthWatts EA500 PSU and EVGA 8600GT graphics card are very quiet.

The loudest noise is air flow noise relating to the rear fan, and that is kind of puzzling. It seems to mostly be coming from the rear fan, but it decreases when I open the case, and decreases even more when the fan is on its own and not mounted there. Maybe noise is from the fan blades stalling aerodynamically because they're working against too much pressure? I'm also left wondering how much of the noise is generated from airflow elsewhere vs. generated at the fan and escaping elsewhere. So, would a quieter fan help much, or do I need to enlarge the front bezel air intakes, as some other people have done? I'm also a bit tempted to cut out the rear fan grille.

Reducing airflow worries me because this motherboard has terrible thermal monitoring. There are only two sensors on it: one at the CPU, and another at a location I don't know. I'm not confident that they would tell me about any hotspots that develop.

The motherboard does have good CPU fan control, but no other fan control in the BIOS. It seems I have one channel of the IT8718F chip available for additional PWM fan control, which I could use to control a PWM fan from SpeedFan. It's also possible to program that chip so it handles fan control without software intervention. I found a program to do that.

After that, it would make sense to deal with are the hard drive and the CPU cooler. Thanks for reminding me about hard drive suspending. I've also seen that enabling AAM quiets this drive a lot. Using an SSD for the OS plus enabling AAM on this drive would be nice. As for CPU coolers, I see that many are compatible with various sockets, so I can get a cooler that will be useful in the future.

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